Is USB-C audio better than using usb c to 3.5mm headphones jack

That would be hard to say. At some point the digital signal needs to be converted to analog. So it would just depend on which device has the better DAC for converting.

I doubt you would hear a difference unless one DAC is very low quality.

Audio through the USB-C port will be better than the jack because the digital signal allows audio to be transmitted more accurately in comparison to the analogue signal transmitted through a 3.5mm audio jack.